High-vacuum multistage distillation method and apparatus



Aug. 5, 1952 LUTEN, JR 2,606,146

HIGH-VACUUM MULTISTAGE DISTILLATION METHOD AND APPARATUS 3 Sheets-Sheet 1 Filed June 26, 1948 INVENTOR'.

DANlEL B LUTEN JR.

HR: ATTORNEY Aug. 5, 1952 LUTEN, JR 2,606,146

HIGH-VACUUM MULTISTAGE DISTILLATION METHOD AND APPARATUS Filed June 26, 1948 3 Sheets-Sheet 2 FIG. Z

INVENTOR:

H63 BY HIS ATTORNEY DANIEL B. LUTEN, JR.

Aug. 5, 1952 0. B. LUTEN, JR

HIGH-VACUUM MULTISTAGE DISTILLATION METHOD AND APPARATUS Filed June 26, 1948 3 Sheets-Sheet 5 LLQ FIG. 5

INVENTOR m J v N. E fl/m o U L kk L m E H m VI B Patented Aug. 5, 1 952 "UNITED STATES PATENT QFFICE 2,606,146 V f HIGH VACUUM MULTISTAGE DISTILLATION a METHOD AND APrAna r s y Daniel BhLuten, Jr., Berkeley, Calif assignor to Shell Development Company, San Francisco,-

Calif a corporation of Delaware Application Julie 26, 1948, Serial N0. 35,340 V V- This invention relates to the art of highvacuum distillation, and, .more particularly, a distillation method and to distillation apparatus wherein vaporization is effected from a liquid flowing as a film over a warm surface (the liquid constituting, the film-being herein referred to as the distilland), and. the resulting vapors pass through an evacuated space toa cold surface on which condensation or all of a major portion of the vapors is effected. Such distillation is, in certain forms involving passage of the vapors through a short, unobstructed path between the warm and cold surfaces, also known as molecular distillation. The present invention, while intended for molecular distillation technique, is not restrictedto operations which achieve true molecular distillation conditions, but may be applied to near-molecular operating-conditions as understood in the art, e.. g,, wherein the vacuum is insufiiciently low or. s'creens-or'the like are placedin the path between the'warm. and cold surfaces so that thisfpathfis. not :quite :unobstructed, or wherein. condensation is'eifected on a plurality of cold surfaces arranged in 'a series, etc. The invention is, however, restricted -tooperation involving condensation of the vapors on a separate, colder surface, and operations of this type will herein',.for the sake of brevity, be designated as high-vacuum, surface-condensation distillations'rifi Such high-vacuum, surface-condensation apparatus are, in the conventional forms, not readily adaptable for fractionation, i. 'e., for repeated re-distillations wherein distillate is flowed as reflux from stagelto stage, and it is for this reason customary to employ a series of such highvacuum, surface-condensation stills, interconnected in accordance with some scheme for achieving.fractionation,when it is desired to effectseparations of a higher order than can beeffected by one stage. (See U. S. Patents Nos. 2,073,202 and 2,128,223.) Accordingto a proposal of Hickman (U..S. Patent No. 2,234,166) in ternal reflux. is attained .by gravity flow from an inner, stationary condensing ,surface' onto an outer, spinning, frustro-conical evaporatingsurface; such an arrangementpalthough useful in certain instances, is, not readilygadapted .for

forced feed or accelerated flowofthe condensate,

and imposes certain "limitations on the design of does not permit the independent the still, e. g., it selection of the rates of reflux, rate of flow of the distilland, and the heights of the stages. Moreover,; the diameter of the'vaporizing surface becomes unduly great when more than a very 'z'olaims. (01. 202-405) small number of stages are. used, resulting in a large, inconvenient rotor and tending to form dry spots on the vaporizing surface;

This invention has for its object the provision of an improved method and apparatus for highvacuum, multi-stage, surface-condensation distillation wherein thedistilland and the condensate (or distillate) are flowed through a succession of stages in a manner to provide reflux of the distillate internally of the still, such reflux being effected by centrifugal-force. s

A further object is to provide .a high-vacuum, multi-stage, unobstructedpath distillation apparatus and method for vaporizing the more volatile constituents, of a distillandfrom amoving'or stationary warm surface; and condensing vapors thus formed one moving, cold surface arranged to transfer the resulting condensate to the warm surface of a differentistage, for vaporization of at least a part of isuch'condens'ate in said other stage together with distilland from said other stage or from a preceding stage,

Another object is to provide an improved highvacuum, unobstructed path distillation apparatus and method wherein the condensate is made to rise within a stage andis transferred to another stage by centrifugal force made effective by revolving an, upwardly diverging, frustro-c'onical condensing surface on which the vapors are condensed and on the, outer surface ofwhichthe condensate is made to-rise, a

Still another objectisto provide'an improved high-vacuum distilling apparatus of the surfacecondensation type comprising a plurality of outer stationary or moving evaporating surfaces so arranged with ,respect to ,ieaehother than; unevapr orated distilland orliquid residues, i. e.', refluxing liquid, will pass generally downwardly within the apparatus from the nth to the -n+ 1th stage, etc,

to the laststage' (passingeither downwardly or upwardly within any one stage, along the outer surface), each of 'said'outer surfaces having facing it an inner,-cold rotating'condensating surface, with means for --causing the condensate collected on said cold surface to ascend and to be transferredfrom-the nthto the n1th stage, etc., upwardly i f 2 These and other objects,which will become apparent from the following description, areattained according to this invention by flowing the I distilland alongan outer, annular heated surface (which may be stationary or revolving, and which may be cylindrical or made up :of a series of frusto-conical sections) and transferring the portion of the distilland remaining unevaporated after passage through one stage to the succeeding stage. The vapors flow generally radially inwardly across an annular, highly evacuated space and are for the most part condensed on a cooled, rotating cendensing surface formed as an inverted frustrum of a cone, 1. e., diverging upwardly. The condensate collects as a film on the cooled surface and is given a' centrifugal force due to the rotation of the surface. This force is counteracted by centripetal force normal to the surface (radially inwardly and upwardly) due to surface tension. The resultant of theseforces causes the film of condensate to travel upwa if'dly along the surface until it reachesthe top of its distillation stage, from where it is transferred to another stage and commingled' with distilland;

r i i mediate stage, depending upon the 'comthis commingling may take place on a heated surface of the new stage, or in a separateimixing stage, as desired. According to a modified form of the invention, the centripetal force is made effective at least a part by providing gutters on the condensing surface, such. an arrangement being desirable particularly when the ascending film of condensate has too. low a surface tension oris too thick to be retained. on the cooled surface by surface tension. alone. r I a The invention will be better understood by reference to the accompanying drawings forming a part of this specification and illustrating certain preferred embodiments of the invention, it being understood that these embodiments are merely illustrative of certain apparatus in accordance with the invention'andnot restrictive of the scope of the invention.

In the drawings:

Fig. l is a vertical, sectional view of a still adapted to effect fractionation .with high-vacuum, surface condensation in accordance with the invention; 1

Fig. 2 is a fragmentary elevation view of a modified form of the rotating condensingsurface; j

Fig. 3 is a transverse sectional. view taken on line 3.-3 of Fig. 2; and. 7

Figs. 4 and 5 are fragmentary, vertical, sectional views of two modified forms of stills according to the invention.

Referring to Fig. 1 of the drawing in detail, designates a cylindrical casing having a'gastight bottom llv and a. gas-tight lid l2. Evacuating conduits [3 in the lid are connected to a suitable source of high vacuum (not shown). A series of outer, annular sections I 4, having frusto-conical walls, are fixed within the casing ID, the inner surfaces of these sections forming the hot vaporizing surfaces and subdividing the- For convenience in assembling still into stages. these sections may be formed separately to nest as shown. The lowest section-Ma has an outer cylindrical flange for making a seal against the casing wall and is supported bya spacer ring l5; Each section provides an annular; horizontal shelf or tray [6 at the base or widest portion of the frusto-conical surface, and is provided with an integral annular dam orweir I! at its radially inner edge; Residence time of distilland' can be controlled by selectioncf theweir height. The lowest section Ha has 'a rim at its inner edge which does not function as a weir. The uppermost section [4b is incomplete in that it has a tray but no frusto-conical wall; it is provided with an outer cylindrical flange forming a seal against the casing wall, and forming an outer rim for retaining liquid on the tray. The trays l6 and fru tb-conicarwalls position of the feed material and the fractionationto be effected. In the embodiment shown, feed material is introduced through a valvecontrolled supply pipe I 9 to the tray of an inv termediate stage.

The condensing surface is formed by a rotor, arranged within and, preferably, concentrically within the sections [4. The rotor comprises a composite vertical shaft having upper and lower sections 20 and 2|, respectively, journalled at the top in a sleeve bearing 22 and at the bottom in a tapered roller bearing 23. The lower section 2| is welded. to" the upper section 20, and is sealed against the bottom II by a suitable packed, gas-tight gland 24; it carries a pulley- 25 by means of which it may be rotated. The lower end extends into a casing 26. The upper section 20 has a central bore 20a extending from a point near the top and opposite to the uppermost stage, communicating with a pipe 21 fixed to the lower section 2|" and extending downwardly through a larger bore 2la therein. The casing 26 is provided with a suitable gland. and flow arrangement for placing the pipe 21 into flow communication with discharge conduit 28' and placing the annular portion ofthe bore 2la surrounding :the pipev 21 into communication with-the supply conduit 29;

Acylindrical tube 30 is fixed to the shaft 20 2! by means of radial tubes 3| at the top and radi'al tubes 32 at the bottom, and one or more intermediate collars 33 with solid radial arms,

Thetube carries a plurality of rotor sections 34,

corresponding in numberto the sections I4- I 4a. The sections are of identical construction- (except for the upper perforations 3.4a) and provide' outer, inverted frusto-conica-l. walls, theouter surfaces of which form the condensingsurfaces. The sharp, upper edge. at the. widestqportion of each rotor is slightly above the top of the nearest weir I 1 of the. stationary sections ll.

Each section has an upstanding rim. or flange, engaging the tube 30, to. which it may be so,-

The upper walls, carryouter, annular raised portions to permit, nesting of the successive sections, as shown.

curedby screws, welding, etc.

Each wall except that of the uppermost. section has perforations 34a providing communication for the flow of a coolingfiuid; An annular plate 35 seals off the bottom of the lowest section andhas an outer depending rim extending overthe inner rim of the. section Illa, but.ro.-

tatable'with respect thereto. Since the space within the casing land within the tube 30' is.

to be maintained-at a high vacuum, while the bore of the-shaft 20' and space outside of thetube 3]! and inside ofthe sections 34 is to be maintained at a somewhat higher pressure (to permit circulationof a cooling fluid) the several sections and plate 35- should be sealed with gas-tight seals with respect to each other, and the inner, upstanding flange at least on the atomic uppermost section andon the'plate 35 should be similarly sealed tothe tube '30. This may be effected; for example, by welding the composite rotor and lowering it into the casing l0.-

Condensateor distillate may be withdrawn from the uppermost tray IB'through a valved discharge conduit 36, and distillation residue from the lowest tray it through a discharge conduit 31. These, may be" provided with discharge ters of mercury, or at a pressure of less than 1 mm., such as, for instance, 0.1-0.001 mm., by applying vacuum to the lines l3; Cooling fluid is circulated through supply conduit 29, flowing thence throughannular space 2Ia, outwardly through tubes 32, up through the successive sections 34, inwardly through tubes 3|, downwardly through'bore Zilagand pipe 27, and out through discharge conduit 28. The frusto-conical and horizontal walls of the sections l4 are heated by heaters i8. Liquid to be distilled is supplied through supply 19 and is heated thereon, a portion vaporizing therefrom and the excess overflowing the weir l1 and descending by gravity as a fllm along-the heated'frusto-conical surface. Due to the high" vacuum and the temperature, volatile constituents are vaporized and move away from this descending film. The unevaporated distilland is collected on the tray l6 immediately beneath as a shallow pool, from which additional evaporation and overflow take place. In this manner the distilland traverses successively the several vaporizingsections or stages. The final, unvaporized residue is withdrawn from the lowest tray via conduit-31.

Within each stage a major portion ofthe vaporized matrialis condensed on the nearest condensing surface, i. e., on the outer surface of the nearest revolving section 34. Theoondensate forms'a thin filmon the cooled surface and is retained therein by surface tension; The centrifugal force resulting from the rotation causesthe condensate film to move upwardly along the cold surface until it reaches the widest portion.- There it is discharged tangentially, moving over the nearest weirl1 and dropping onto the corresponding tray I6, wherein it is mixed with distilland entering the tray from the next higher vaporizing surface. To maintain vaorizing liquid on the hot surfaces above the stage into which the feed liquid is supplied it is necessary to provide reflux; this may be provided by'throttling the valve in the conduit 36 to withdraw only a portion of the'material discharged onto the uppermost tray 14b. However, it is also possible to introduce reflux from an voutside, source, such as a surge tank.

Referring to Figs. 2 and 3, inclined gutters '38 may be provided on the outer surface of the condensing-sections 34, the rotor being assumed to rotate in the direction indicated by the arrows. These gutters collect the condensate and lift it, somewhat in the manner of a screw lift. Upon reaching the top of a section 34 the condensate is flung tangentially outwardly onto the nearest tray [6. It will be noted that the gutters have their concave surfaces leading, i. e., disposed toward the direction of travel. As previously indicated, it is also possible to heat the vaporizing surface by means of a heat-v ing fluid, and/or use a rotating vaporizing sur-1 face, so as to effect a controlled rate of'the distilland. A still embodying both of these" features is fiuustratedin rig; ggfwhich-shows only a few tri e i term di te s ages fv the till. it b i understood that the shaft may be mounted for rotation and for feeding and discharging heating 'and'coolingfluids by a construction "of the type described indetail in connection with Fig. 1.

In Fig.4, the rotor shaft 20' has a bore ZUa for cooling liquid and carries two concentric tubes 30 and 40. "The's'ections 34'fof the cooling sections are fitted to'the tube '30 andare provided with ports 34a;for"circulation'of icooling fluid, as in Fig; '1. 'The annular' spaces 4| and 42 between tubes 30*a'nd 40,'and between tube 40 andshaft 20,respectively,-are;however, sealed off for the circulation of heating fluid.

The vaporizing surfaceis formed of inverted. -frusto-conical,-hollow sections 43 mounted on and rotatable with the cooling sections. These up- "wardlyl diverging vaporizing sections may be supported by any structural elements, for example, by means ofradial pipes'44 and. The pipes 44 interconnect the annular-space "4! with the bottom of'each hollow space within'the sections 43, and serve to supply heating fluid to the vaporizing'sections. The pipes 45 interconnect the annular space'42 with the top of each hollow space and serve to return heating fluid from the vaporizing sections. The, lowest, narrowest portion of each vaporizingsection extends slightly below the uppermost; widest portion of the corresponding cooling section 34.

' The outer casing lli'carries stationary annular gutters --46 for collecting unvaporized distilland from the top of each vaporizing section. Each gutter is'p'rovided with-one or more downspouts 41 for discharging liquid from the gutter onto the vaporizing surface-of the next lower stage. The downspouts 41 are stationary and their lower ends-arelocatedsothat liquid dropping down will fall on the rotating vaporizing surface a short distance above the bottom of the vaporizing section. 7

'Material to be distilled maybe introduced into I any stage of the still, either an end stage or an intermediate stage, e. g., through a feed conduit 48.

' In operation. the rotoris revolved, the casing i0 is evacuated, and cooling fluid is circulated, as described for Fig. 1. plied upwardly through the annular space 4| and the radial pipes 44 to the spaces within the hollow vaporizing sections'43, and is then discharged through the pipes 45 and the annular space 42. The distilland forms a thin film on each vaporizingsurface and rises due'to centrifugal force. Volatile constituents are vaporized from the distilland and are-condensed'on the sections 34, and unvaporized distilland, upon reaching the top of a vaporizing section, is flung tangentially out- I wardly into the nearest gutter 46. From there it is conveyed by the'downspout 41 to the next lower stage. The condensed volatile material riseson the, outer condensingsurface of the sections 34 and, upon reachingthe uppermost edge. is flung tangentially outwardly onto the bottom of the vaporizingsurface of the next higher stage. Distillation residue and distillate are eventually withdrawn from the bottom and top of the column, respectively, as described for Fig. l, for example through conduits-communicating with the nearest gutters.

It should be noted that byproceeding in the manner just described. distillate'istransferred from the nth stage to the 11.- 1th stage, where it Heating fluid'is supac ess is commingled wlthdistilland residue transferred through a downspout'fromfthe' fi-QZth stage to the nrursrage; 'Kflowjrelationshipof thet'ype employed. conventional;fractionation i'sflihereforejachieydi- As befo e indicated, the embodiment shown. in Fig'.' ramerely illustrative, and subject. to modifications.".'l?lius,..ji nstead' of providing hollow vaporiziiflgjsections'hatd by a heatingfiu'id,'simple thin-metal'frustoiconifcall sectionsheatedby radiah'theat. 'e..g electric elements. such. as the 'elements l8. ofliigfll' niayibe employed.

v According? td 'stillanother embodiment, shown in'Fig. '5,fthe vaporizing surface is. the inner face of a. stationary j'wall'. 49 carried by and spaced from the casing 10 torrents an annular space 50 through which heating fluid. is circulated upwardly; The rotor comprisesa. hollow shaftZfl, cylinderf3fl, and cooled. inverted frusto-conical condensing set'ztionsfilt, as before. 'Thesections 3 4 however, have. annular'isolating. shields 5| extending from 'the widest part,.to which annular gutters 52 arefixedl .Each shield, carries one QrLmore upwardly 'asasutwamly inclined upspouts 53 communicating with the topof the gutter and terminating. near'the vaporizingsurface, just beneath thenext higher isolating shield 5| and, hence, near the top of the next superior stage. Liquid. tov bedi'stilled may be introduced at any stage ofthe still, for example, through a supply pipeil'coimected to. an annular, perforated distributing pipe5'5 having av deflector 56'. Liquid issuing fronitheperforations of the pipe 55. by gravity are directedtoward the cylindrical vaporizing surface to form. a.- film thereon. The pipe. 55 isfspaced'fr'om the vaporizing surface to avoid obstructing the downward flow" of distiliand from higher stages, GuttersEl and 58 at the top and bottom permit condensate and distillation residue to. be withdrawn. via conduits 59 and. 6 Refluxis provided by throttling valve In the. embodiment according to Fig. 5- the vaporizing surface is continuous, but may be regarded as comprising a plurality of stages, the; boundaries of. which are fixed byadjacent isolatii'lg-shields- 51,- In operation, the casing [0 is evacuated, the rotor is placed in motion, and heating. and cooling fluids are circulated as previously'describ'edg Distilland flows down the va porizing' s'urface'from stage to stage. Within cachrstage a portion of the distillandisvapori'z'ed and major portion .thereof condensed on thej'conderising surface of. the respective section 34. whereonitmoves upwardly as a Upon reaching the topof asection. 3.4 it is discharged into the gutter and" moves from. there upwardly through the upspout 53,v impelled by centrifugal force. From the topgf'the upspout thecondensate is discharged tangentially against the vaporizing surface near the top of the next. higher stage, being there ccmmingled: with. unvaporized distilland from. thc..:s tage above that. It will be noted that condensate. froman nth stage is 'commingled with-.nnva'porized distilland from the n-2th stage,,, as previously described.

The condensing sectiona according to Figs. 4 and'.5"may be modified as shown in- Figs. zand 3-; It is obvious-that, by the arrangement described in this specification; it is possible to select the areas for, the several vaporizing surfaces to accommodatejth'e dlstilland at the respective sections, for efxample, by making different condensing, sections and/or vaporizing s a e id fiefe ti e I. claim as. myinvent'ion: Y

1.. Fractional distillation apparatus comprising a. substantially vertical tubular member having an inner vaporizingsurface, means'for forming a film of distillandcn said surface, mean for heating said surface, a rotor shaft within said tubular member substantially coaxia1 therewith and having a bore communicating to the outside of the tubular member, a plurality of thin-walled condensers spaced from said shaft to provide flow spaces for the flow of cooling fluid and rotatable with the shaft, said condensers being distributed 'over'th'e major portion of the length of said tubular member, each condenserhaving an outer condensing surface that'extends upwardly and outwardly from the axis of the shaft, means for rotating the shafttothrowcondensate upwardly and. tow'ardsaid vaporizing surface by the resultantfcentrifugal force and interfacial tension, a substantially horizontal. annular wall surrounding said shaft between each adjacent pair of condensers. for separating said flow spacesfrom eachother, said walls having openings interconnecting said flow spaces in a series for the flow of" cooling fluid successively through said flow spaces, a communicating passageway between the bore of thesh'aft and a flow space near one end of the shaft, conduit meansconcentric with said shaft and isolated from said here communicating with the flow space near the other end of the shaft and with the outside of the tubular-member, and means. for circulatingcooling fluid from the outside of the tubular member through said bore, flow spaces and conduit means and thence to the outside of the tubular member.

2, Fractional distillation apparatus comprising a substantially vertical tubular member having an inner vaporizing surface, means for forming a film of distilland on said surface, means for heating said surface,a rotor within said tubular member substantially co-axial therewith having condensing means distributed over the major portion ofthe. length of said tubular member and havingasurface rotatable with the rotor and extending upwardly and outwardly from its axis, an inclined gutter onsaid condensing surface, and me'ans for rotating the rotor to lift condensate and throw condensate toward said vaporizing surface. by the resultant of centrifugal force, interfacial tension and the action ofsaid gutter.

3'..A high-vacuum; unobstructed path, fractional distillation apparatus having ;a series of superposed stages comprising anouter, downwardly-divergent, frusto-conical wall in each stage forming, a vaporizingsurface on the inner face. thereof, an. annular, substantially horizontal tray joining the top of each of said walls-with the bottom of the wall of the next higherstage, arrangedto cause distilland to traverse successive stages in sequence by flowing downwardly as a film along each frusto-conical vaporizing surface and radially inwardly over the intervening trays, means for heating, said outer walLa; rotor withinsaid outer. wall having, within each stage, awsn-romun 'o its outer face an upwardlydivergent, frusto-conical condensing surface spaced from said vaporizing surface, said condensi'ng' surface extending upwardly to a height above the tray of the next higher stage, whereby condensate-collected on said condensing surface is, during operation, lifted thereon bycentrifugal force and discharged-tangentially outwardly over said tray into the said next higher stage, conduit means'for introducing. material to be distilled, mean's' for'removing condensate from. an upper stage, means for separately removing unvaporized distilland from a lower stage, and means for evacuating the space between the vaporizing surface and the condensing surface.

4. A high-vacuum, unobstructed path, fractional distillation apparatus having a series of superposed stages comprising a vertical casing, an outer, stationary, downwardly-divergent conical wall in each stage forming a vaporizing surface on the inner face thereof, an annular, substantially horizontal tray joining the top of each of said walls with the bottom of the wall of the next higher stage, an annular weir at the radially inner edge of each tray for distribut ing liquid, said walls, trays and weirs being arranged to cause distilland to traverse successive stages in sequence by flowing outwardly as a film over successive walls and across successive trays in shallow pools, means for heating said outer wall and trays, a rotor within said outer wall having, within each stage, a wall forming on its outer face an upwardly-divergent, frustoconical condensing surface spaced from said vaporizing surface, said condensing surface extending to a height a small distance above the weir of the next higher stage, whereby condensate collected on said condens ng surface is during operation lifted thereon by centrifugal force and discharged tangentially outwardly over said weir into the next higher stage, conduit means for introducing material to be distilled onto one of said trays, means for removing condensate from an upper tray, means for removing unvaporized distilland from a lower tray, and means for evacuating the space between the vaporizing surface and the condensing surface.

5. A high-vacuum, unobstructed path, fractional distillation apparatus having a series of superposed stages comprising a casing, a plurality of rotatable, upwardly-divergent, frustoconical walls within said casing forming vaporizing surfaces on the inner faces thereof and providing said stages, means for heating said walls, conduit means for introducing liquid to be distilled onto the inside of one of said vaporiz- 1 i ing surfaces so that, during operation, it is caused to flow thereover upwardly by centrifugal force, means for transferring unvaporized distilland from the top of a vaporizing surface onto the bottom of a subsequent, lower vaporizing surface, a

a plurality of rotatable walls, arranged one within each stage, forming on their outer faces upwardly-divergent, frusto-conical condensing surfaces spaced from said vaporizing surfaces, each of said condensing surfaces extending to a height a small distance above the bottom of the vaporizing surface of the next higher stage, whereby condensate collected on said condensing surface is lifted thereon by centrifugal force and discharged tangentially against the vaporizing surface of said next higher stage, means for removing condensate from an upper stage, means for separately removing unvaporized distilland from a lower stage, and means for evacuating the space between the vaporizing surface and the condensing surface.

6. A high-vacuum, unobstructed path, frac tional distillation apparatus comprising a casing, a vertical rotor within said casing supporting a plurality of upwardly-divergent, frusto-conical walls forming vaporizing surfaces on the inner faces thereof and defining a plurality of super-- posed distillation stages, means for heating said walls, conduit means for introducing liquid to be distilled onto the inside of one of said vaporizing surfaces so that, during operation, it is caused to flow thereover upwardly by centrifugal force, an annular gutter on said casing for each stage located to collect unvaporized distilland from the top of each vaporizing surface, means for transferring distilland from each gutter onto the bottom of the vaporizing surface of the next subsequent, lower stage, a plurality of walls on said rotor forming on their outer faces upwardlydivergent, frusto-conical condensing surfaces spaced from said vaporizing surfaces, each of said condensing surfaces extending to a height a small distance above the bottom of the vaporizing surface of the next higher stage, whereby condensate collected on said condensing surface is lifted thereon by centrifugal force and discharged tangentially against the vaporizing sur-- face of said next higher stage, means for removing condensate from an upper stage, means for separately removing unvaporized distilland from a lower stage, and means for evacuating the space between the vaporizing surface and the condensing surface.

7. A high-vacuum, unobstructed path, fractional distillation apparatus having a series of superposed stages comprising an outer wall forming a vaporizing surface on the inner face thereof, means for heating said wall, a rotor within said outer wall having, within each stage, a wall forming on its outer face an upwardly-divergent, frusto-conical condensing surface spaced from said vaporizing surface, collecting means at the top of each condensing surface for collecting condensate including a downwardly directed annular member, whereby condensate collected on said condensing surface is, during operation, lifted thereon by centrifugal force and introduced into said collecting means, conduit means having a radially inwardly directed face for transferring condensate from said collecting means upwardly by centrifugal force and flow along said face and discharging it against the vaporizing surface near the top of a higher stage, conduit means for introducing material to be distilled onto said vaporizing surface, means for removing condensate from an upper stage, means for separately removing unvaporized distilland from a. lower stage, and means for evacuating the space between the vaporizing surface and the condensing surface.

DANIEL B. LUTEN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,321,801 Bausman Nov. 18, 1914 1,141,898 Merritt June 1, 1915 1,688,297 Parent Oct. 16, 1928 2,128,223 Fraser Aug. 30, 1933- 2 .234,166 Hickman Mar. 11, 1941 2,313,175 Scott Mar. 9, 1943 2,446,997 Brewer et al. Aug. 17, 1945 2,406,421 Wollner et al. Aug. 27, 1946 OTHER REFERENCES Ayers, Separation by Centrifugal Force, copyright 1942, by the Sharples Corporation 

1. FRACTIONAL DISTILLATION APPARATUS COMPRISING A SUBSTANTIALLY VERTICAL TUBULAR MEMBER HAVING AN INNER VAPORIZING SURFACE, MEANS FOR FORMING A FILM OF DISTILLAND ON SAID SURFACE, MEANS FOR HEATING SAID SURFACE, A ROTOR SHAFT WITHIN SAID TUBULAR MEMBER SUBSTANTIALLY CO-AXIAL, THEREWITH AND HAVING A BORE COMMUNICATING TO THE OUTSIDE OF THE TUBULAR MEMBER, A PLURALITY OF THIN-WALLED CONDENSERS SPACED FROM SAID SHAFT TO PROVIDE FLOW SPACES FOR THE FLOW OF COOLING FLUID AND ROTATABLE WITH THE SHAFT, SAID CONDENSERS BEING DISTRIBUTED OVER THE MAJOR PORTION OF THE LENGTH OF SAID TUBULAR MEMBER, EACH CONDENSER HAVING AN OUTER CONDENSING SURFACE THAT EXTENDS UPWARDLY AND OUTWARDLY FROM THE AXIS OF THE SHAFT, MEANS FOR ROTATING THE SHAFT TO THROW CONDENSATE UPWARDLY AND TOWARD SAID VAPORIZING SURFACE BY THE RESULTANT CENTRIFUGAL FORCE AND INTERFACIAL TENSION, A SUBSTANTIALLY HORIZONTAL ANNULAR WALL SURROUNDING SAID SHAFT BETWEEN EACH ADJACENT PAIR OF CONDENSERS FOR SEPARATING SAID FLOW SPACES FROM EACH OTHER, SAID WALLS HAVING OPENINGS INTERCONNECTING SAID FLOW SPACES IN A SERIES FOR THE FLOW OF COOLING FLUID SUCCESSIVELY THROUGH SAID FLOW SPACES, A COMMUNICATING PASSAGEWAY BETWEEN THE BORE OF THE SHAFT AND A FLOW SPACE NEAR ONE END OF THE SHAFT, CONDUIT MEANS CONCENTRIC WITH SAID SHAFT AND ISOLATED FROM SAID BORE COMMUNICATING WITH THE FLOW SPACE NEAR THE OTHER END OF THE SHAFT AND WITH THE OUTSIDE OF THE TUBULAR MEMBER, AND MEANS FOR CIRCULATING COOLING FLUID FROM THE OUTSIDE OF THE TUBULER MEMBER THROUGH SAID BORE, FLOW SPACES AND CONDUIT MEANS AND THENCE TO THE OUTSIDE OF THE TUBULAR MEMBER. 